ACTIONSCRIPT 3 Developer’s Guide en

ACTIONSCRIPT 3.0 DEVELOPER’S GUIDE
Working in three dimensions (3D)
The UV 0 and 1 locations on a bitmap image
Vectors of a triangle can be given UV coordinates to associate themselves with the respective locations on an image:
The UV coordinates of a triangular area of a bitmap image
The UV values stay consistent with the points of the triangle:
The vertices of the triangle move and the bitmap distorts to keep the UV values for an individual point the same
As ActionScript 3D transformations are applied to the triangle associated with the bitmap, the bitmap image is applied
to the triangle based on the UV values. So, instead of using matrix calculations, set or adjust the UV values to create a
three-dimensional effect.
The Graphics.drawTriangles() method also accepts an optional piece of information for three-dimensional
transformations: the T value. The T value in uvtData represents the 3D perspective, or more specifically, the scale
factor of the associated vertex. UVT mapping adds perspective correction to UV mapping. For example, if an object is
positioned in 3D space away from the viewpoint so that it appears to be 50% its “original” size, the T value of that object
would be 0.5. Since triangles are drawn to represent objects in 3D space, their locations along the z-axis determine their
T values. The equation that determines the T value is:
T = focalLength/(focalLength + z);
In this equation, focalLength represents a focal length or calculated "screen" location which dictates the amount of
perspective provided in the view.
Last updated 6/6/2012
365